1. Field of the Invention
The invention concerns a ceramic foam body that can be used as a buoyant member of a boom for containing an offshore oil spill, either while the oil is burned off or until the oil can be taken away for disposal. Among other uses, the novel ceramic body can be a fire-resistant building material.
2. Description of the Related Art
An effective technique for the disposal of offshore spilled oil is to burn off the oil while it is confined within a floating fire-resistant boom. This technique can dispose of oil layers as thin as 1 to 2 mm but is more effective for thicker layers which can be burned with efficiencies in excess of 95%.
A fire-resistant boom of U.S. Pat. No 4,537,528 (Simpson) includes a flotation member such as plastic foam or cork surrounded by at least two layers of heat-resistant, water-sorbent material such as woven glass fibers that extend into the water in the form of a dependent skirt. The bottom of the skirt is formed with a loop for receiving a tensioning chain. Water drawn up by the skirt is said to keep inner layers of the boom free from fire damage. Unfortunately, booms that depend upon wicking can lose as much as fifty percent of their buoyancy during use. It is understood that a bottom-tensioned, cylindrical-flotation, fire-containment boom has been manufactured by Fire Control Inc. utilizing teachings of the Simpson patent.
A fire-resistant boom of U.S. Pat. No. 4,923,332 (Sanocki et. al.) has a flotation core (15) consisting of a closed-cell foam log (18) wrapped in a knitted wire mesh (19) and a heat conducting metal foil (20). The foam log can be a glass foam or borosilicate ceramic foam, the former being preferred because of cost and availability. The flotation core is surrounded by a heat insulating spacer (14). The spacer can be a wire mesh that has been knitted to form a plurality of pockets, each of which is filled with ceramic foam spheres that are impermeable to water and so contribute to the buoyancy of the boom. Covering the spacer are a tightly woven ceramic textile fabric (13), a knitted wire mesh (12), and a polymer-coated fabric (11) that is formed with a pocket (17) to receive a ballast chain. When used to contain burning oil, so much of the outer polymer-coated fabric that extends above the water line can burn away without the boom coming apart, because the three outer layers are fastened together below the water line, and the woven ceramic textile fabric (13) continues to hold the assembly together.
The Sanocki boom is currently marketed by 3M Co. as "3M Fire Boom" in 50-foot (15.2-m) lengths with seven sections, each section containing two end-to-end glass foam logs, each 91.5 cm in length. The boom has adequate flexibility between sections to permit it to be arranged in a zig-zag pattern of straight, side-by-side sections. When so laid out on a deck of a ship, the boom can be payed out to be deployed around an oil spill. The section lengths are chosen for convenience in shipment to permit the boom to be transported on a highway with the sections extending between the sides of the truck.
Although the Sanocki boom is highly effective, it is inherently expensive, and the voids in its spacer can become filled with water, thus reducing its buoyancy. When its foam log is glass to reduce the cost, the glass foam can be damaged by heat encountered during oil burnoff, thus reducing its buoyancy to the point that the boom might sink. Furthermore, the ceramic foam spheres of the outer buoyancy member are not very strong and might be crushed when the boom is forced against hard objects while being towed.